1. Field of the Invention
The present invention relates to a wideband active circuit with a feedback structure applicable to an amplifier, a mixer, or the like, and more particularly, to a wideband active circuit with a feedback structure for feeding back a signal of an output terminal to an active load to thereby improve bandwidth.
2. Description of the Related Art
In general, as expected requirements for a data transfer rate are increasing in a broadcasting or communications system, the bandwidth of both a digital and an analog circuit needs to be sufficiently assured.
In addition, in the case of an amplifier configured as a short channel device, if a gate length of a transistor increases, the gain is thereby increased, but an RC time constant value also increases, thus reducing bandwidth. Thus, it is of critical importance to obtain a high gain and a wide bandwidth while consuming less power.
For an amplifying circuit corresponding to the related art active circuit, there are several methods for increasing bandwidth, and among them, a feedback technique and a Miller capacitance cancellation using a cascade transistor are commonly used.
Among the feedback methods for improving the bandwidth of the related art active circuit, a resistive feedback reduces the gain, while a capacitive feedback has a limitation in increasing bandwidth, although it can increase the bandwidth without a gain reduction.
Meanwhile, in case of Miller capacitance cancellation using a cascade transistor which has high output resistance, it is difficult to obtain much gain in terms of bandwidth unless an input pole is dominant.